The former Prime Minister’s comments, in a blogpost on his website and a series of television interviews, opened fresh wounds within the party over the 11-year-old Iraq war.

Sources close to Ed Miliband refused to endorse Mr Blair’s analysis. One told the Independent: “What matters now is making the judgements rather than seeking to make points about what happened in the past.”

The shadow Foreign Secretary, Douglas Alexander, echoed the Coalition Government’s view that military action is not contemplated. He said: “The truth is that it is the Iraqis themselves who hold the key to resolving this crisis.”

Interviewed on BBC1’s Andrew Marr Show, Mr Blair made clear he was not advocating the deployment of ground troops, but said western nations should “actively try and shape this situation with our allies in the region”.

In the article on his website, the former Labour leader insisted the latest bloodshed in Iraq was not linked to the invasion.

He blamed the re-emergence of extremist fighters on the weakness and sectarianism of the Iraqi government, as well as the failure to intervene in neighbouring Syria, which has been embroiled in civil war for more than three years.

His comments were condemned by his former deputy, Lord Prescott, who spelt out his opposition to Britain’s involvement in Iraq in 2003 and accused him of wanting to launch a “crusade” in the region.

Lord Prescott told Sky News: “I said to him at the time, your great danger, when you want to go and do these regime changes, you’re back to what Bush called a crusade…Put on a white sheet and a red cross, and we’re back to the crusades. It’s all about religion – in these countries it’s gone on for a thousand years.”

He dismissed the use of drones as “not a way for Britain to go in the name of open society”, adding: “Hardly democratic either. So I don’t agree with Tony as I didn’t then.”

She called him a “complete American neocon” who had been “absolutely consistently wrong, wrong, wrong” on the issue.

Sir Christopher Meyer, Britain’s ambassador to the US from 1997 to 2003, said the handling of the campaign to remove Saddam was “perhaps the most significant reason” for the sectarian violence now convulsing Iraq.

“We are reaping what we sowed in 2003. This is not hindsight. We knew in the run-up to war that the overthrow of Saddam Hussein would seriously destabilise Iraq after 24 years of his iron rule,” he wrote in the Mail on Sunday.

The former Liberal Democrat leader Lord Ashdown said: “I’m having a bit of a difficulty getting my mind round the idea that a problem that has been caused or made worse by killing many, many Arab Muslims in the Middle East is going to be made better by killing more with western weapons.”

Robert Fisk: How does Tony Blair get away with his lies? Assad’s enemies, whom Blair’s bombing of Damascus would have helped, now threaten Iraq: here.

TONY BLAIR, who is understandably opposed to the full transcripts of all of his talks with President Bush being published in the Chilcot Inquiry report into the Iraq war, has told the BBC that his illegal war with Iraq is in no way responsible for the current collapse in Iraq: here.